With the rapid development of science and technology and the continuous improvement of manufacturing techniques and product structures, ball valves, created in the 1950s, have rapidly developed to be one of the main valves within only 40 years. In western industrially developed countries, ball valves have been increasingly used year by year. In China, ball valves are extensively applied to industries like petroleum refining, long-distance transport pipes, chemical engineering, papermaking, pharmacy, water conservancy, electric power, municipal administration, iron and steel and the like, and occupy a unique position in national economy. The conventional rigidity seal ball valve has the advantages as follows: I, wear resistance: as the valve element of a rigidity seal ball valve is made of alloy steel by spray welding, and the sealing ring of the rigidity seal ball valve is made of alloy steel by build-up welding, the rigidity seal ball valve is less prone to too much wear and tear during opening and closing operations. II, long service life and wide application range: the conventional rigidity seal ball valve has been widely applied to petroleum, chemical engineering, power generation, papermaking, atomic energy, aviation, rockets and other divisions, as well as people's daily life. However, with the progress of society and the advance of science and technology, higher requirements on the rigidity seal ball valve are put forward, that is, the rigidity seal ball valve could still work normally at an ultra-high temperature for a long period of time, while a soft seal ball valve is prone to leakage of a sealing ring or seal seat at a temperature exceeding 250 DEG C. The conventional rigidity seal ball valve can work normally at the maximum temperature below 550 DEG C. Working under a high temperature or ultra-high temperature condition may easily result in deformation of a valve rod or a ball body. Once the valve rod deforms, working staff or a motor cannot drive the valve rod to move, the ball body cannot be opened or closed normally, great potential safety hazards may be caused; once the ball body deforms, the sealing performance of a product may easily become poorer, thereby ultimately causing a potential leakage risk.